1. Field
This disclosure relates to an electrode for generating plasma and a plasma generator for depositing a thin film on a substrate.
2. Description of the Related Art
During chemical vapor deposition (CVD) or atomic layer deposition (ALD), simultaneous application of precursors and plasma is often required. Plasma may be generated by applying voltage between two or more electrodes facing each other. FIG. 1 is a schematic view showing a conventional plasma generator. The plasma generator includes electrodes 101, 102 facing each other, and a power source 103 for applying voltage between the electrodes 101, 102. One electrode 101 includes protruding threads 110 with sharp ends. When voltage is applied by the power source 103, plasma 104 may be generated between the protruding threads 110 and the electrode 102.
When a flat-type electrode is used, capacitive type plasma may be generated. However, the capacitive type plasma needs a low pressure of about 1 Torr or below. It is difficult to generate the capacitive type plasma at an atmospheric pressure. In order to generate plasma at an atmospheric pressure or a relatively high pressure (for example, greater than about 100 Torr), dielectric barrier discharge (DBD) or pulse corona discharge is generated, and thus, the electrode 101 has the sharp protruding threads 110 to generate plasma using DBD or pulse corona discharge.
But plasma is generated only in a region in proximity to the protruding threads 110 of the electrode 101. Hence, the uniformity of plasma is less than desirable. To improve the uniformity of plasma, method of adjusting the arrangement or number of electrodes 101, 102 is proposed. But even this method does not ensure excellent uniformity of plasma.
FIG. 2 is a schematic view showing another conventional plasma generator. The plasma generator of FIG. 2 includes two electrodes 201, 202 having concentric cross-sections, and a power source 203 for applying power between the two electrodes 201, 202. One electrode 201 may be located within the other electrode 202. The inner electrode 201 may have an uneven surface. At this time, plasma 204 may be generated between the outer electrode 202 and a protruding thread 211 of the inner electrode 201.
In the plasma generator of FIG. 2, the sharp protruding thread 211 is used to generate DBD or pulse corona discharge. Hence, plasma is not uniformly distributed on a substrate 200. In order to improve the uniformity of plasma, the arrangement or number of electrodes 201, 202 may be adjusted. But this method does not produce uniform radicals because concentric arrangement may not be easily obtained and plasma is not generated at the center of the electrode 201.